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Experimental deformation of chalcopyrite single crystals at 200°C
Tectonophysics, Elsevier
217
135 (1987) 217-232
Science Publishers
B.V., Amsterdam
Experimental
- Printed
in The Netherlands
deformation of chalcopyrite at 200%
CHRISTA HENNIG-MICHAEL1 ftir Mineraiogie und Lagenstiittenlehre,
Institut
(Received
August
and HEINRICH
R WTH Aachen,
30,1985;
single crystals
Wiillnerstmsse
revised version
accepted
SIEMES of Germany]
2, D-5100 Aachen (F.R. May 29,1986)
Abstract Hennig-Michaeli,
C. and Siemes, H., 1987. Experimental
Martens,
I. van der Molen,
Processes
on a Macro-
Prismatic
specimens
2OO”C, 300 MPa discriminating
Eight different
The specimens
deformation,
and assignment
The height
rate
the pseudocubic
of chalcopyrite R.L.M.
Vissers
a large natural
crystal
structure,
surfaces
In: H.J. Zwart,
Tectonic
s-l.
to a specific quadrant
M.
Structural
within confines
deformed
Orientation
out by X-ray
of between
by means
texture
goniometry
a stereographic
tested by
0.7% and 2.3%.
of interference projection
the glide directions
at
determinations
[021], 12211, [421], [821]-were contrast
and of the sense of glide steps allows determination
of slip steps further
and
were experimentally
were carried
axial shortenings were inspected
crystal 4. lop6
[lOOI, [llO], [ill],
to permanent
single crystals. (Editors),
135: 217-232.
of approximately
orientations-[OOl], specimen
of the glide direction
of the crystal.
cut from
a strain
of glide line orientations
and
Tectonophysics,
CuFe!$, and
were subjected
pre-polished
analysis
top surface
pressure
[OOl] and [lOO] within
compression. After
of chalcopyrite,
deformation
C. Spiers
Meso- and Micro-Scale.
confining
using 103-reflections.
Two-surface
C.W. Passchier,
methods.
of the glide plane
that is drawn
which are assumed
from the
to be along
low index lattice lines. The main deformation bands
mechanism
and fine slip lines of remarkably
behaviour.
They
all agree
crystallographically l/2(311) partials.
with
equivalent
straight
except
character
the [OOl]-sample,
often extend
(112}(3ii)
slip and
{112}(311)
but the critical
resolved
shear stresses
= 0.986 nm is large The formerly
in all specimens,
predicted,
and it is expected
that
“sphalerite-like”,
the crystal
slip, respectively. are similar,
the dislocations
slip directions
was by slip on (112).
throughout
would
(liO>,
Coarse
slip
a planar
slip
The two slip modes
about undergo
(021)
indicating
80 MPa
are not
The Burgers
a complex
are not consistent
dissociation with
vector into
the recent
observations. In the [OOl]-specimen character
in sections
across
{112}(11~)
twinning
N1 and are straight
was the main in sections
along
glide mode.
The twins
Nt. The twinning
exhibit
a pronounced
wavy
shear stress was 115 MPa.
Introduction
Chalcopyrite structure
Chalcopyrite (CuFeS,) is the most common copper mineral and in places it occurs in massive ore bodies which can show a variety of deformation microstructures. The aim of this paper is to elucidate the deformation mechanisms in chalcopyrite. This work is part of a more extensive study on the influence of temperature on the plasticity of chalcopyrite single crystals.
The crystal structure of CuFeS, (space group symmetry 142d) can be described as a superstructure of sphalerite with cO G 2a, (Pauling and Brockway, 1932). The orientations of prominent planes and directions in chalcopyrite are depicted by a stereogram in Fig. 4. Chalcopyrite is noncentrosymmetric, so that poles on the upper hemisphere are not crystallographically identical with
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B.V.
218
those on the lower hemisphere. In the chalcopyrite rounded
ments
structure
tetrahedrally
each sulfur is sur-
by two Cu atoms (Cu-S
0.230 nm) and two Fe atoms (Fe-S In the pseudocubic each sulfur
face centered
is shifted
(Hall and Stewart, occupied Stewart,
was not
= 0.226 nm).
sulfur sub-lattice
away from Cu towards
Fe
1973). The plane most densely
is considerably
covalent
CU~+F~~+(S~-)~
as
Cu’Fe3+(S2-), (Shuey,
rather
crystal
known.
1975) the orientation
axes to the applied
Stress-strain
data
had
The statements
by Kelly
(1975) that
{112}(liO)
{112}(021)
and
modes
neither been
and
of chalcopyrite
of stress
nor had the glide directions
determined.
the deformation
Clark
slip are were not
substantiated. Nevertheless, these previous experiments have shown that slip as well as twinning
(Hall and
1973) and the ionic approximation
considered
and Clark,
been established
by atoms is { 112) (Fig. 1).
The bonding be
=
(Kelly
the tetragonal
should
occur on { 112). Twinning
than
elevated
1975).
temperatures
seems to be favoured
(300°C
Kelly
and
at
Clark,
1975). The strength
of polycrystalline
chalcopyrite
de-
Natural chalcopyrite fabrics
creases from about 500 MPa at room temperature
Cataclastic fracturing, deformation twins, elongation of grains and distinct preferred orientations, subgrains and fine-grained recrystallized aggregates have all been reported from natural deformed chalcopyrite ores (Kom, 1933; Shadlun, 1953, Ramdohr, 1980; Cox and Etheridge, 1984). The majority of chalcopyrite ores, however, is totally recrystallized into mosaics of lobate to equant grains with no obvious internal deformation features.
Roscoe, 1975; Kelly and Clark, 1975). As found in single crystals both slip and twinning occur on { 112). At room temperatures slip and cataclasis predominate (Lang, 1968) whereas with an increase in temperature twinning gains in importance, and is dominant between 200°C and 300° C. Above 300” C slip is again prevalent (Atkinson, 1974). Coarse slip lines occur up to 200°C at fast strain rates, whereas at higher temperatures and lower strain rates, slip lines tend to accumulate in patches within the grains (Roscoe 1975). The loss of strength, increase in ductility and decrease in cataclasis, from room temperature
to about
Previous deformation
experiments
between
[@iI
Fig. 1. Crystal
at 500°C
(Atkinson,
200°C
and
3OO’C. Above
boil
(112)
structure
of chakopyrite.
1974;
up to 300°C are inferred to result from the increase in deformation twinning (Kelly and Clark, 1975). Subgrain development was seen to start
Compression experiments on chalcopyrite crystals at room temperature have shown that (112) is the main glide plane (Miigge, 1920; Buerger, 1928; 1930). As in more recent experi-
Cu S Fe S
100 MPa
Arrangement
of atoms and lattice vectors
in (112)
150°C
the
219
experimental pirical
data can be characterized
power
law with
(n = 8.6; Roscoe,
a high
by an em-
stress
exponent
1975).
Starting material The present natural Nababeep
along
of minute
geneities.
single
West Mine,
2). Fractures lines
studies were made utilizing
chalcopyrite
Besides
pores
crystal
Cape Province, (112)
cleavage
Short lattice vectors of chalcopyrite, space group 142d (100) = 0.5291 mn l/2 (111) = 0.6417 mn (110) = 0.7482 nm l/2 (311) = 0.9875 nm [OOl]= 1.0427 nm
the
RSA (Fig. planes
are macroscopic
a larger
a large
from
TABLE 1
polycrystalline
and
Orientation determination
inhomoDue to the pseudocubic
pyrite
chalcopyrite,
Laue
arrangement back
reflection
of atoms
aggregate, sporadic sphalerite grains ( < 30 pm) were found in the undeformed crystal which contains no twins and has a low dislocation density.
in
patterns
along [OOl] and from each other.
(100) cannot be distinguished Reflections of the type h k 21
The chemical composition Cu,,,Fe,,O,S, was established by microprobe analyses and is in good agreement with that of common chalcopyrite, cul.Ol-1.02F%00-1.02 S, (Cabri and Hall, 1972).
and I k 2h have structure factors cubic reflection goniometry the
similar lattice plane spacings and so that they scatter almost like a hkl. By means of X-ray texture orientation of chalcopyrite (Laue
The lattice constants are a, = 0.5291 nm and c,, = 1.0427 nm and thus are up to 0.2% larger than those determined by Cabri and Hall (1972) and Hall and Stewart (1973). Short lattice vectors are listed in Table 1.
group 4/mmm) can be established when a reflection is taken with 1 # 2n and h + k # 2n, cf. 101, 103, 321 (Hennig-Michaeli and Herres, 1985). These weak reflections are superstructure reflections when compared to sphalerite. The 103 reflection has been used in the present work. The Liicke-texture goniometer plots pole diagrams in stereographic projection (Fig. 3). Specimen preparation During cutting and polishing the chalcopyrite crystal behaves in a brittle manner. The crystal was embedded in araldite such that the crystal directions [221], [321] and [02i] were parallel to the edges of the araldite block. The embedded crystal was cut parallel to (112) into two pieces by a rotating grinding blade (thickness 1.7 mm, u = 32 m s-l) which is usually employed to slice stressfree optical glasses. From one piece several slices parallel to (li0) and (012) were cut off in a high precision hole saw (blade thickness 200 pm, u = 25
Fig. 2. Natural chalcopyrite single crystal. Nababeep West Mine, Cape Province, RSA. On the top of the crystal an inclusion of a pyrite aggregate. Scale mark 1 cm.
m s-l). The slices were mounted between glass plates and prism-shaped specimens (7 x 7 x 14 mm3) were cut by a low speed diamond saw. Three of the four prism surfaces were grounded (Sic) and polished (Al,O,) by hand with successively finer grades down to < 1 pm. Surface cavities could not be removed in all cases (see Fig. 8c,
220
Fig. 3. Orientation CoK,
= 35.9O)
projection
from
determination (001) and
(SP), upper hemisphere
of chalcopyrite (100) faces.
(Laue
Besides
symmetry
103 reflections,
4/mmm).
Liicke
112 reflections
pole
figure
(2@ CoK,
goniometer
plots
= 34.2O) appear.
of 103 (26’ Stereographic
(UH).
d). The polished surface areas were checked by interference contrast observations to be free from fine scratches. After re-exa~nation of the orientation a specimen coordinate system x, y, z was defined for each crystal (see Figs. 8a, 9a, lOa). Experimental procedure
The program assumes homogeneous axial strain which, in reality, never occurs during single crystal tests of this kind. In particular, in this series of experiments the strain is usually concentrated in coarse slip bands distributed inhomogeneously within the crystal. Thus the stress-strain diagrams outline but do not clearly define the deformation behaviour.
Apparatus Compression The triaxial compression apparatus used in this series has been previously described in detail (Bauer, 1973) and briefly sketched (HennigMichaeli and Siemes, 1982). The confining pressure medium is silicone oil. The test sample is encapsuled in an aluminium jacket and a platinum foil is inserted between the chalcopyrite and the aluminium to prevent surface reactions and to make easier removal of the jacket from the deformed crystal. The jacket is fixed to conical end pieces by steel rings.
Measurements During the run, load, displacement, and confining pressure are recorded in chosen time increments (60 s). The rate of displacement is approximately kept constant by regulation of the load increment. Stress-strain curves are derived from the data records by means of a computer program taking into account the specimen dimensions and the elastic distortion of the apparatus.
tests on chalcopyrite single crystals
All experiments confining pressure
were performed at 300 MPa as previous experiments, cited
above, had shown that up to 200 MPa the strength of chalcopyrite is dependent on confining pressure. The temperature of deformation was 200°C (0.41 T,) and the strain rate about 4. 10m6 s-r. There was not any evidence of phase transformations or de-sulph~~on during the experiments. Eight different orientations-[OOl], [IOO], [lIO], [ill], [021], [221], [421], [821]-were tested. In Fig. 4 the size of the circles representing the compression axes approximately characterizes the range of inaccuracy in the crystal o~entation as determined by texture goniometry. The permanent axial shortening of the samples was between 0.7% and 2.3% (see Table 4). The samples were only deformed to this extent as experience has shown that at low permanent strains the glide line patterns on the crystals can be more readily analyzed than those on strongly deformed specimens. In addition the determination of
221
Determination of glide modes
Fig 4. Crystallography of chalcopyrite. SP. Planes and directions (black points), compression axes (open circles).
Burgers vectors by TEM is facilitated if there is only a moderate dislocation density within the deformed crystal. The stress-strain curves display a marked anisotropy of the plastic behaviour of chaleopyrite (Fig. 5). “Weak” directions are [NO] and [021], “strong” directions are [llO], [OOl] and [221]. Marked strain hardening characterizes the [ill] direction whereas, in the [OOl] direction, the curve seems to indicate steady-state flow behaviour.
Conditions: T
= 200°C
pc = 300 MPa E
0
I’ 0
= 4.10-6s“
I
I
I
I
I
05
1
15
2
25 E I%1
Fig. 5. Stress-strain
curves of chaicopyrite single crystals.
In order to understand the plastic behaviour of a crystal, careful observation of the surface structures is required, as it gives fund~ent~ evidence of the material displa~m~t during deformation. The aim of the present work is to determine the glide modes by analysis of the strained crystals. The assumption was made that the glide planes are low index lattice planes and that the glide directions are low index lattice directions with a small Burgers vector. Hypothetical and crystallographically non-equivalent glide modes of this kind are listed in Table 2, together with the S&mid factors for the eight compression directions used in these experiments. In this study defo~ation twins were distinguished from slip lines by measuring the 112 reflection in the X-ray pole figure goniometer (Fig. 10e). Glide planes, glide line structures
When there are prominent sets of glide lines that can be traced from one surface to an adjacent one, it is possible to determine the glide plane by the angles they make with the edge between the two surfaces (Reed-Hill, 1968). In all specimens glide on (112) has been the predominant deformation mechanism. There are two different kinds of (112) glide lines. Very coarse straight bands characterize slip, whereas (112) deformation twins are more or less wavy depending on the surface they occur on. On the [OOl] specimen only (112) twins have been observed. In. all other samples {1123 slip is prevalent. On the [221] oriented specimen homogeneously distributed wavy glide lines indicate another slip plane in the zone ]liO] and in the [llO] sample faint short lines in more strongly deformed areas suggest a slip plane in the zone [OOl]. On all specimen surfaces the (112) slip bands are of the same kind. They are always straight and indicate a planar slip behaviour. The thickness of the bands varies up to maximum of 40 pm. This is interpreted to indicate a mechanism of dislocation multip~cation in adjacent slip planes so that the
222
223
overall
slip occurs in sets of closely spaced planes.
Between
the slip bands
fected by deformation The
exterior
the material
appears
Y
unaf-
tanIp
(e.g., see Fig. 9c, d).
of the
(112)
slip
bands,
trace
con-
= of
a, / ey glide
direction
sistently similar on all surfaces, suggests that { 112} slip in all specimens was due to the same or almost
the same slip mode. To determine
direction,
the slip band characteristics
the slip
were studied
in detail. Determination
Fig. 7. Crystal distortion.
Extensions
e,,
e., along the speci-
mens axes x, y indicate the direction of the trace of the main glide direction in the x-y
plane + = dy,
trace of glide direc-
tion.
adjacent specimen faces allow an estimation of the angular range of the slip direction on a particular
of the slip direction in (112)
Owing to the coarse character of the (112) slip bands the sense of the slip steps on the prepolished surfaces can be easily determined by interference contrast optical microscopy. The sense of the slip steps indicates whether at a slip band the part of the crystal above the line (sense a) or the part of the crystal below the line (sense b) is displaced towards the observer (Fig. 6). When the slip plane is known the senses of the slip steps as observed on the two adjacent crystal faces allow assignment of the direction of material transport and, thus, the direction of the Burgers vector, to a specific quadrant in the stereogram of the crystal top face. The height of the slip steps further confines the possible slip directions. The slip steps are of small height and display a weak relief when the slip direction is oriented close slip steps and a stronger slip direction at a high surface. The relative relief
to a surface and higher relief is produced by a angle to the specimen of sets of slip lines on
slip plane. Crystal distortion After deformation the dimensions of the crystals were remeasured. The shortening e, along the compression axis z as well as the extension e,, ev normal
to the prism
faces provide
the basis
of
determining the bulk material transport during deformation. The ratio eJe,, is an approximate measure of the anisotropy of plastic strain. If only one predominant (112) slip system in a crystal has been active, the angle r$ (Fig. 7) indicates the direction of the trace of the glide direction in the x-y-plane. Determination (CRSS)
of the critical resolved shear stress
The yield strength of the crystal is taken as the stress at the first strong departure from the elastic portion of the stress strain curve. The glide system, represented by the highest density of glide lines on the crystal the CRSS: Identification
surfaces,
is used to determine
of slip systems
in the deformed
crystals Three examples of deformed single crystals have been selected to illustrate how the glide modes have been determined.
Fig. 6. Sense of glide steps. Sense a: the part of the crystal
Compression
axis [l 1 O]
Specimen y = [OOl].
axes (Fig.
(I bove the line is displaced towards the observer; sense b: the part of the crystal observer.
below
the line is displaced
towards
the
8a):
z = [llO],
x = [ilO],
224
L
f
[1101
11
X
b
Malt. slip A
a
d
,1
mm
,
pole
plane
225
Crystal distortion The main slip system on (112) chiefly caused the crystal distortion. The strain due to other slip systems is negligible. Due to the symmetrical arrangement of the slip planes (112) and (112) to the [llO] compression axis, a specific hypothetical {112} slip mode would produce identical ex/eY ratios whatever the slip mode, e.g.:
Slip-line pattern (Fig. 8c-fl On the (ilO) surface four kinds of (112) slip lines are apparent indicating that four different slip systems have been activated. The morphology of the lines are the same in aII cases; they are straight and more or less coarse. The slip bands are directed along (112) and (112) traces. In each direction, sets of lines with mutually opposite senses a and b are present, indicating that two different slip systems were activated on one plane.
(112) (iii)
Main slip system Most prevalent are slip bands on (112) with sense a on the surface (ilO>. They extend across the whole specimen and display a rather strong relief on both specimen surfaces, (710) and (001) (Fig. 8c-f). The slip direction of the chief lines on (112) is situated in the orientation range x--J-t as represented by the upper right quadrant of the stereogram in Fig. 8b on the upper hemisphere. Low index directions in (112) with positive S&mid factors and with a corresponding orientation are [ZOi), [?li] and [42i]. [iii] is parallel to the (ilO) surface and would not have produced a marked relief on it (Table 3).
a. Specimen
crystal,
compressed
axes, orientation
(201)
= 0.70
(311)
= 1.37
(421)
= 2.05
Slip mode An unexpected result of this experiment was that {112}@1) slip is not a prominent slip mode (under the given conditions) although 1/2(iil) is the shortest lattice vector in (112) with a high S&mid factor (0.47) in this experiment. (112) (311) slip explains best the observations, but {112}(201) cannot be excluded from being an active slip mode. Crystal strength The [llO] specimen was the strongest of the whole series (Fig. 5). The plastic deformation proceeded discontinuously at growing stress levels. The unsteady plastic behaviour is assumed to correspond to ,the sudden formation of individual slip bands. Each slip band seems to have a specific yield point. The yield strength of the crystal is
along [llO].
of the unit cell.
b. Top face of the crystal. SP/UH. Pole and trace of the main slip plane (ll?). The slip direction -X-y-z. The direction [311] agrees best with the relief of the main lines and the crystal distortion. c. Face (ilO), reflection
micrograph.
Strong
d. Face (OOl), reflection
micrograph.
Medium
e. Detail
from (c), interference
contrast
dark lines are of sense n, due to (llj)[%i] of sense b, due to (112)[131] f. Detail from (d), interference slip. In the heavily
deformed
=0
The ex/ey ratio (1.23) of the deformed crystal most closely fits (311) and hence the main slip system is most likely to be (112) [jli].
Deformation twins Minor twins along (112) and (172) as identified by X-ray texture goniometry are parallel to the compression axis and are thought to be due to stress inhomogeneities at surface imperfections. They are more abundant on the unpolished surface (170) and absent on the polished surfaces (001) and (110). On (OOi) they appear in the surroundings of surface cavities.
Fig. 8. Deformed
eJe,
slip. Faint contrast
(negative
end) lies in the quadrant
Slip mode is {112}(311).
relief of main slip bands. relief of slip bands.
micrograph.
Slip lines along (112) (N55“E)
are due to two different
slip. The light lines of sense b, due to (llz)[l%] traces (E-W) micrograph.
area faint inclined
may indicate
the are
slip on a plane in the zone [OOl], perhaps
All coarse dark slip lines (E-W)
slip traces occur.
(112) slip systems:
slip. Slip lines along (112) (N54OW) {lOO) (010)
are of sense b, due to (ll?)[%i]
slip.
and (ll?)[l?i]
3
Schmid
factors (S) deviate
0.41
[ZOi]
0.48
]jii]+
0.45
slip modes
0.32
]5ii]-
*
’
‘
3ii, 4%)
ones in Table 2.
[iii]-
i
iii).
or of (112}(11i)
0.25
]42i]
0.24
--[Ill].
0.27
[ilo]
0.24
(S)
chakopyrite
Schmid factors
{ 112}(201,~11.421,
from the theoretical
possible
’
0.42
[Zoi]
0.42
[421]
0.32
[4Zl]
0.43
[zoi]
0.37
[ZCij-
0.39
[ZB] -
and experimental
on the deformed
slip modes {112)(2Oi,
]3ii]+
0.37
]3ii]+
0.48
]3ii]-
0.32
0.41 --]3111 0.3% --[131].
possible
slightly
of hypothetically
Experimental
[ uw] ’ is a shear direction
S
S
s
S
s
s
S
of hypothetically
(112)
(112,
(1lZ)
(ii2)
(112)
(ii2)
(i12)
s
--[131]
Possible shear directions
is a shear direction
* [UWJ
I1101
CHX
]lW
CH6
[X211
CH5
]42Ti
CH4
WI
CH3
12211
CH2
11111
CHl
(ii2)
plane
pression
axis
Main
slip
of sense of shear at the main sets of {112} slip bands
Cry&II,
analysis
com-
Two-surface
TABLE *
-twins.
s
S
S
S
s
S
s
s
Excluded
crystals
[iii]-
[201]+
0.48
[iii]
0.49
]42i]
0.46
@oi]+
0.42
+
1
[iio]
0.41
]oZi]
+
0.30
[iii]
[Z41] 0.23
[ilo] 0.41
0.20
[02i].
’
-_[ill] 0.38
[021] 0.29
[ill]*
0.24
[241]
0.28
toii]
0.41
0.42
]4Zi] 0.4Y
0.30
]iio]
0.33
iZ;ii]
*
+
’
[ii01 0.28
[iii]0.29
0.28
[iio]
[Ioil
0.31
0.38
0.40
]o%]
shear directions
221
265 f 5 MPa and the CRSS for the most likely slip mode (112) (311) is about 85 MPa. Compression
axis [021]
Specimen axes (Fig. 9a): z = [021], x = [02x], y = (ioo]. Slip line pattern
(Fig. SC-~).
The slip line pattern appears similar to that of the [llO] sample. However, there are only two kinds of (112) slip bands, one predominant set along (112) and minor slip lines along (712). Comparison of the relief of lines on the two specimens (Figs. 8 and 9) gives evidence of a remarkable difference: Whereas on the [llO] sample the lines appear in almost the same contrast on both surfaces, on the [021] sample the relief is weak on the (012) face and very strong on the (%lO) face, indicating that the direction of slip is close to the (012) face. Minor twins on (712) have been detected by texture goniometry of this sample. Main slip system
On the face (012), the (112) lines are of sense a (Fig. 8e). The slip direction is, again, situated in the orientation range Z-y-z (upper hemisphere, Fig. 9b). Possible slip directions might be [3ii] and [2Oi], but the relief due to a direction close to (Olz), excludes [2Oi].
observations is [3‘ii] and hence {112}(3ii) most likely the slip mode. Crystal strength
The [021] crystal was one of the weakest crystals in the test series (Fig. 5). A stepwise shortening characterized the plastic behaviour Iike in the [llO] crystal, pointing to a corresponding slip behaviour. The yield strength, 175 + 5 MPa, is only two thirds of that of the [llO] crystal. The CRSS for the main slip system, (112) [3ii], is about 84 MPa. The CRSS value, the corresponding slip behaviour and the consistent attributes of the slip bands, in either specimen,- respectively corroborate -the postulation that (112)[311] was the predominent active sIip system in the [llO] specimen. The close agreement of the ratio (0.67) of the reciprocal S&mid factors of the main slip systems in the two samples with the ratio of the yield strengths u,,~OZll/~,,ulOl = 0.66 is believed not to be simply fortuitous. It supports the following conclusions concerning the plastic behaviour of chalcopyrite under the experimental conditions: (a) {112}(~11) and {112}(3ii) are the main slip modes. (b) Although the two slip modes are not crystahographicahy equivalent they have nearly identical CRSS. (c) The S&mid law is obeyed. Compression
Crystal distortion
A strong anisotropy of lateral extension corresponds to the observed surface pattern. eJe,, = 0.23 = arctan 13” only fits the direction [3ii] (Fig. 8b). Slip mode The sense of surface steps excludes [ilO] from
being slip direction. The (llZ)[liO] system was not activated. (112)[2Oi] does not explain the slip band exteriors or the crystal distortion. If {112}(201,2Oi) slip had operated in the two crystals that have been described, the deformed samples would look almost identical. The only direction in (112) that closely fits the
is
axis [l I l]
Specimen axes (Fig. lOa): z = [ill], y = [El] Glide line pattern
x = [ilO],
(Fig. 10~)
Five different sets of glide lines occur, two along (i12), two along (112) and one along (112). Main slip systems
Two sets of long, straight lines result from slip on (112) and (112). They display a distinct relief on both specimen faces. On the (ii2) surface, both sets of slip lines are of sense a. This therefore unequivocally excludes (2Oi) to be slip direction. Although [?Oi] on (i12) and [O%] on (li2) are directions of high Schmid factors in this test
228
a
e
b
ccl12 X
Main slip plane A pale
229
TABLE
4
Compression
tests on chalcopyrite
Sample
Compression
Maximum
Shorten-
Yield
axiS
strength
ing
stress
(MPa)
(W)
(MPa)
265
1.42
180
WI
CHl
single crystals
(temperature
200°C,
confining
pressure
300 MPa, strain
Glide modes
{i12}(3ii) dip
rate about
4. 10m6 s-l)
Schmid
CRSS
factor
(MPa)
0.41
74
(112}(lli)twinmng CH2
[22ll
287
2.27
250
(ll2)(3ii)
dip
0.32
80
{001}(110)
slip (TEM)
0.47
i 120
CH3
[02ll
196
1.00
175
(ll2)(3ii)
dip
0.48
84
CH4
14211
242
1.10
220
{112}(311)
slip
0.37
81
{ll2)(3ii)
dip
CH5
WI
186
0.65
165
{112}(311)
slip
0.45
74
CH6
WI WI w11
186
1.13
165
(112}(311)
slip
0.48
79
294
1.13
265
{112)(?11)
slip
0.32
85
261
1.58
250
{112}(111)twinmng
0.46
115
CH8 CHlO
Crystal strength The yield strength of the sample is low, 180 f 10 MPa, but the strong strain hardening is singular in this test series. In the range of yielding an unsteady flow was observed, but during strain hardening the flow was continuous. The CRSS for {112}(3ii) slip is about 74 MPa and, thus, in agreement with the values obtained from the other crystals (Table 4) within the experimental uncertainties. The interaction of slip and twinning may have caused the more continuous plastic flow as well as the strain hardening.
(Table 3), they have not been slip directions because they are oriented parallel to the (ii2) surface and cannot have produced the marked relief as observed (Fig. 10~). {112}(1iO) can also be excluded, because it would not have produced a strong line relief on the (710) surface. Therefore the best agreement with the observed slip line structures are the two slip systems (i12) [‘;ii] and (172) [i?i], both belonging to the slip mode {ii2)(3ii). Deformation twins X-ray texture goniometry reveals three different orientations of deformation twins (Fig. 10d): (i12), (172) (112) are the twin planes. The exterior of the twins differs markedly from that of the slip lines. The twins are short and wavy. On the (ii2) surface the twins on (i12) and (172) are of opposite sense in comparison to the slip lines (Fig. SC) and agree with (il2)[ili] and (li2)[lii] deformation twinning. {112) (11-i) is the twinning mode. Fig. 9. Deformed a. Specimen
crystal,
compressed
axes, orientation
sullunaly of results Slip modes Slip on (112) was the main deformation mechanism in all specimens except the [OOl] oriented sample. Coarse and straight slip bands indicate a planar slip behaviour. The uniform appearance of slip bands on all respective deformed crystals sug-
along [021].
of the unit cell.
b. Top face of the crystal.
SP/UH.
X-y-z.
agrees best with the relief of lines and the crystal
The direction
[3ii]
Pole and trace of the main slip plane (112). The slip direction
c. Face (Olj), reflection
micrograph.
Weak relief of main slip bands.
d. Face @IO), reflection
micrograph.
Very strong
e. Detail from (c), interference
distortion.
(negative
end) lies in the quadrant
Slip mode is (112}(3ii).
relief of slip bands,
contrast
micrograph.
Slip bands
f. Detail from (d), interference contrast --are of sense a, due to (i12)[311] slip.
micrograph.
Light slip lines (N86 o W) are of sense b, due to (112)[3ii]
along (112) (N55OE)
are of sense a, due to (112)[3ii]
slip.
slip. Dark slip lines
230
b
a
Main glide planes .
poles traces
,
C
Fig. 10. Deformed a. Specimen
crystal,
compressed
axes, orientation
b. Top face of the crystal. directions
200
IUrn
,
d
‘1
along [ill]
of the unit cell. SP/UH.
Poles and traces of the main glide planes
(i12),
(112). (112): slip directions
(s) and twinning
(tw) are indicated.
c. Detail of face (ii2),
interference
contrast
micrograph.
(712) traces (N31°E).
Slip lines are dark and of sense a, due to (i12)[%i]
slip. Twins are light and short and of sense b, due to (i12)[111] twinning. (112) traces (N32O W). Slip lines are dark and of sense a, -__ due to (li2)[131] slip. Twins are light and of sense 6, due to (liZ)[lTi] twinning. (112) traces (E-W). Wavy twins are light and of sense b, due to (112)[11i]
twinning.
d. 112 pole figure goniometer twinning. (il2)
twins:
B-A&C_B-D_B.
(li2)
twins:
C-A_C-B_C-D_C.
(112) twins:
D-A&B_D-CLJ.
plot, face (ii2).
SP/UH.
Host crystal
orientation
is A-B-C-D.
Double
symbol
reflexes
are due to
231
gests a unique operating (112) slip mode. AnaIysis of the senses of slip steps on mutually perpendicular prepolished faces of the prism-shaped samples allows us to exclude other possible slip directions in the principal slip planes (Table 3). The shear along the slip bands and the distortion of the crystals are in accordance with {112}(311) slip or pi2)(3ii) slip, respectively. The anisotropy of yield strength is in agreement with these conclusions. The CRSS is about 80 MPa (Table 4). The Burgers vector l/2(311) is large and moving dislocations should be dissociated. TEM-studies on the samples [llO] and [221] (Couderc and Hennig-Michaeli, 1986) show that the majority of dislocations in (112) remain in contrast whatever the operating g is. Dissociation into up to four partials is observed in weak beam dark field micrographs. Such peculiarities can be explained by the Burgers vector b = l/2(311) although a full characterization of these dislocations has not yet been accomplished. In the [221} oriented crystal (OOl)(llO) slip has been identified by TEM-observations (Couderc and Hennig-Michaeli, 1985). Some cross slip from (001) to (112) occurs, thus explaining the waviness of the corresponding slip traces on the specimen surface. On the [llO] sample faint surface traces may indicate a slip plane in the zone [OOl]; they are possibly due to (100) (010) slip (Fig. 8e). In the vicinity of surface inhomogeneities, minor slip lines, mostly along (112) traces, do not agree with the shear due to the main slip modes. Deformation
twinning
{112}(11i) deformation twinning was the principal deformation mechanism in the [OOl] sample and important in the [ill] sample. K, is not yet known but with analogy to sphalerite it is assumed to be (ii2). The state of the specimen surface obviously has an effect on the origin of (112) twins. X-ray texture goniometry shows that twins are more abundant on non-polished surfaces than on prepolished ones. On prepolished surfaces they tend to start at surface inhomogeneities, e.g., cavities.
On the [221] oriented crystal, twins proceed from the (110) (110) surfaces, but are nearly absent on (114) and (ii4). The twins are long and straight on surfaces parallel to the twinning direction and short and wavy on faces mutually perpendicular. Thus, the shapes of the twins resemble blades of swords, the twinning direction representing the long axis about which the blade is wrinkled. From the shape of the twins, it can be inferred that {112}(11i) twinning dislocations can move easier if they are of edge character than if they are screw dislocations. TEM-studies reveal numerous immobile screw segments of twin dislocations pinned at the boundaries of microtwins (Couderc and HennigMichaeli, 1986). Twinning, as a unique glide mode does not give rise to any strain hardening, as displayed by the flow behaviour of the [OOl] sample. The interaction of slip and twinning has probably caused the strong strain hardening in the [ill] sample. The twins in the [ill] crystal originated at lower shear stresses (< 85 MPa) than those in the [OOl] crystal (115 MPa). These results show that there does not seem to be a CRSS for this type of mechanical twinning in chalcopyrite. Discussion
The slip modes {112}(311) and {112}(3ii) are the models which explain the experimental observations better than all other hypothetically possible slip modes on (112). Contrary to expectations, (112) slip in chalcopyrite agrees neither with the shortest Burgers vector 1/2(iil) in {112}, nor with the previously predicted slip directions (110, 021). Such {112}(liO, 021) slip postulates pseudocubic slip behaviour which would have given rise to similar results for the compression tests on [OOl]-[loo], [ill}-[421] and [llO]-[021]. The experimental results are not at all consistent with this “sphalerite-like” model, but indicate that the deformation mechanisms are controlled by the tetragonal lattice and, hence, by the cation sublattice.
232
Acknowledgements
The Deutsche Forschungsg~me~s~haft supported this research and placed at our disposal the deformation equipment and the texture goniometer. A.F. Lombaard and Mr. Engelbrecht (Ookiep Copper Company) supplied the single crystal. G. Neidull (Ernst Leitz Wet&r GmbH) and H. Oepen (Philips Research Laboratory, Aachen) helped to cut the crystal. The staff of the Mineralogical Institute rendered practical assistance, in particular A. Wiechowski, B. Thiele (microprobe analysis), G. Siebel (X-ray diffraction), W. Grawinkel (poising), G. Prapotny, M. Brandt (apparatus), M. Jansen (photographs) and 3. Huppertz (crystal preparation and data processing). The work benefited from discussions with N. Herres, H.C. Heard, L. Martens, L. Kiibler and J.J. Couderc. The help of these persons and institutions is gratefully acknowledged. Thanks are due to two anonymous referees for their constructive criticism of the manuscript. References Atkinson, B.K., 1974. Experimental deformation of polycrystalline galena, chalcopyrite and pyrrhotite. Inst. Min. Metall. Trans., Sec. B, 83: B19-B28. Bauer, G., 1973. Experimentelle Stauchverformung an otztaler Glimmerschiefem. Diss. Rheinisch-WestfUischen Hochschule Aachen, 127 pp. Buerger, M.J., 1928. The plastic deformation of ore minerals Am. Mineral., 13: 35-51. Buerger, M.J., 1930. Translation gliding in crystals. Am. Min., 15: 45-64. Cabri, L.J., and Hall, S.R., 1972. Mooihoekite and haycockite, two new copper-iron sulfides and their relationship to chalcopyrite and talnakhite. Am. Mineral., 57: 689-708. Couderc, J.J. and Hennig-Michaeli, C., 1985. Evidence for (001) (110) slip in experimentally deformed chalcopyrite by TEM-observations. Forts&r. Mineral., 63 (Beih. 1): 45. Couderc, J.J. and Hennig-Michaeli, C., 1986. Transmission electron microscopy of experimentally deformed chalcopyrite single crystals. Phys. Chem. Miner., 13: 393-402.
COX,SF. and Etheridge, M.A., 1984. Deformation microfabric development in chalcopyrite in fault zones, Mt. Lyell, Tasmania. J. Struct. Geol., 66: 167-182. Hall, S.R. and Stewart, J., 1973. The crystal structure refinement of chalcopyrite, CuFeS,. Acta Cryst., B29: 579-585. Hennig-Michaeli, C. and Herres, N., 1985. Orientierungsbestimmung experimentell erzeugter Deformationszwillinge nach (112) und {102} im Chalcopyrit &Fe% mit Hilfe des Lbcke-Texturgoniometers. Forts&r. Miner., 63 (Beih. 1): 94. Hennig-Michaeli, C. and Siemes, H., 1982. Experimental deformation of hematite crystals between 25’C and 400°C at 400 MPa confining pressure. In: W. Schreyer (Editor). High-pressure Researches in Geoscience. Schweizerbart, Stuttgart, pp. 133-150. Kelly, W.C. and Clark, B.R., 1975. Sulfide deformation studies. III. Experimental deformation of chalcopyrite to 2000 bars and 500°C. Econ. Geol., 70: 431-453. Kom, D., 1933. Ein deformiertes Flusspat-Quar-Kupferkiesgefbge aus einer mittelschwedischen SulfidlagerstBtte. Neues Jahrb. Mineral., Geol., Pahaontol., Beil., A66: 433-459. Lang, H., 1968. Stauchversuche mit poly~$t~~nen Kupferkiesen und deren Ergebnisse unter Beticksichtigung der Gefigeregelung. Diss. RWTH Aachen, 131 pp. MUgge, O., 1920. ijber Translationen am Schwefel, Periklas und Kupferkies und einfache Schiebungen am Boumomt, Pyrargyrit, Kupferglanz und Silberkupfer~~. Neues. Jahrb. Mineral., Geol. Pal%ontol., pp. 24-54. Paul& L. and Brockway, L.O., 1932. The crystal structure of chalcopyrite CuFeSz. Z. Kristallogr., 82: 188-194. Ramdohr, P., 1980. The Ore Minerals and Their Intergrowths. Pergamon Press, London, 2nd ed. 1205 pp. Reed-Hill, R.E., 1968. Crystallographic techniques to determine the indices of slip and twinning. In: R.F. Bunshab (Editor), Techniques for the Direct Observation of Structure and Imperfections. In: Techniques of Metals Research, Vol. II, Part 1. Interscience, New York, N.Y., pp. 257-290. Roscoe, W.E., 1975. Experimental deformation of natural chalcopyrite at temperatures up to 300°C over the strain rate range lo-’ to 10v6 s-r. Econ. Geol., 70: 454-472. Shadlun, T.N., 1953. The change in the structure of aggregates and in the internal structure of grains of chalcopyrite subjected to the influence of dynamic factors. Mineral. Sb., Lvov. Geol., Ser. 7: 75-80. Shuey, R.T., 1975. Semiconducting Ore Minerals. Elsevier, Amsterdam, 415 pp.
217
135 (1987) 217-232
Science Publishers
B.V., Amsterdam
Experimental
- Printed
in The Netherlands
deformation of chalcopyrite at 200%
CHRISTA HENNIG-MICHAEL1 ftir Mineraiogie und Lagenstiittenlehre,
Institut
(Received
August
and HEINRICH
R WTH Aachen,
30,1985;
single crystals
Wiillnerstmsse
revised version
accepted
SIEMES of Germany]
2, D-5100 Aachen (F.R. May 29,1986)
Abstract Hennig-Michaeli,
C. and Siemes, H., 1987. Experimental
Martens,
I. van der Molen,
Processes
on a Macro-
Prismatic
specimens
2OO”C, 300 MPa discriminating
Eight different
The specimens
deformation,
and assignment
The height
rate
the pseudocubic
of chalcopyrite R.L.M.
Vissers
a large natural
crystal
structure,
surfaces
In: H.J. Zwart,
Tectonic
s-l.
to a specific quadrant
M.
Structural
within confines
deformed
Orientation
out by X-ray
of between
by means
texture
goniometry
a stereographic
tested by
0.7% and 2.3%.
of interference projection
the glide directions
at
determinations
[021], 12211, [421], [821]-were contrast
and of the sense of glide steps allows determination
of slip steps further
and
were experimentally
were carried
axial shortenings were inspected
crystal 4. lop6
[lOOI, [llO], [ill],
to permanent
single crystals. (Editors),
135: 217-232.
of approximately
orientations-[OOl], specimen
of the glide direction
of the crystal.
cut from
a strain
of glide line orientations
and
Tectonophysics,
CuFe!$, and
were subjected
pre-polished
analysis
top surface
pressure
[OOl] and [lOO] within
compression. After
of chalcopyrite,
deformation
C. Spiers
Meso- and Micro-Scale.
confining
using 103-reflections.
Two-surface
C.W. Passchier,
methods.
of the glide plane
that is drawn
which are assumed
from the
to be along
low index lattice lines. The main deformation bands
mechanism
and fine slip lines of remarkably
behaviour.
They
all agree
crystallographically l/2(311) partials.
with
equivalent
straight
except
character
the [OOl]-sample,
often extend
(112}(3ii)
slip and
{112}(311)
but the critical
resolved
shear stresses
= 0.986 nm is large The formerly
in all specimens,
predicted,
and it is expected
that
“sphalerite-like”,
the crystal
slip, respectively. are similar,
the dislocations
slip directions
was by slip on (112).
throughout
would
(liO>,
Coarse
slip
a planar
slip
The two slip modes
about undergo
(021)
indicating
80 MPa
are not
The Burgers
a complex
are not consistent
dissociation with
vector into
the recent
observations. In the [OOl]-specimen character
in sections
across
{112}(11~)
twinning
N1 and are straight
was the main in sections
along
glide mode.
The twins
Nt. The twinning
exhibit
a pronounced
wavy
shear stress was 115 MPa.
Introduction
Chalcopyrite structure
Chalcopyrite (CuFeS,) is the most common copper mineral and in places it occurs in massive ore bodies which can show a variety of deformation microstructures. The aim of this paper is to elucidate the deformation mechanisms in chalcopyrite. This work is part of a more extensive study on the influence of temperature on the plasticity of chalcopyrite single crystals.
The crystal structure of CuFeS, (space group symmetry 142d) can be described as a superstructure of sphalerite with cO G 2a, (Pauling and Brockway, 1932). The orientations of prominent planes and directions in chalcopyrite are depicted by a stereogram in Fig. 4. Chalcopyrite is noncentrosymmetric, so that poles on the upper hemisphere are not crystallographically identical with
0040-1951/87/$03.50
Q 1987 Elsevier Science Publishers
B.V.
218
those on the lower hemisphere. In the chalcopyrite rounded
ments
structure
tetrahedrally
each sulfur is sur-
by two Cu atoms (Cu-S
0.230 nm) and two Fe atoms (Fe-S In the pseudocubic each sulfur
face centered
is shifted
(Hall and Stewart, occupied Stewart,
was not
= 0.226 nm).
sulfur sub-lattice
away from Cu towards
Fe
1973). The plane most densely
is considerably
covalent
CU~+F~~+(S~-)~
as
Cu’Fe3+(S2-), (Shuey,
rather
crystal
known.
1975) the orientation
axes to the applied
Stress-strain
data
had
The statements
by Kelly
(1975) that
{112}(liO)
{112}(021)
and
modes
neither been
and
of chalcopyrite
of stress
nor had the glide directions
determined.
the deformation
Clark
slip are were not
substantiated. Nevertheless, these previous experiments have shown that slip as well as twinning
(Hall and
1973) and the ionic approximation
considered
and Clark,
been established
by atoms is { 112) (Fig. 1).
The bonding be
=
(Kelly
the tetragonal
should
occur on { 112). Twinning
than
elevated
1975).
temperatures
seems to be favoured
(300°C
Kelly
and
at
Clark,
1975). The strength
of polycrystalline
chalcopyrite
de-
Natural chalcopyrite fabrics
creases from about 500 MPa at room temperature
Cataclastic fracturing, deformation twins, elongation of grains and distinct preferred orientations, subgrains and fine-grained recrystallized aggregates have all been reported from natural deformed chalcopyrite ores (Kom, 1933; Shadlun, 1953, Ramdohr, 1980; Cox and Etheridge, 1984). The majority of chalcopyrite ores, however, is totally recrystallized into mosaics of lobate to equant grains with no obvious internal deformation features.
Roscoe, 1975; Kelly and Clark, 1975). As found in single crystals both slip and twinning occur on { 112). At room temperatures slip and cataclasis predominate (Lang, 1968) whereas with an increase in temperature twinning gains in importance, and is dominant between 200°C and 300° C. Above 300” C slip is again prevalent (Atkinson, 1974). Coarse slip lines occur up to 200°C at fast strain rates, whereas at higher temperatures and lower strain rates, slip lines tend to accumulate in patches within the grains (Roscoe 1975). The loss of strength, increase in ductility and decrease in cataclasis, from room temperature
to about
Previous deformation
experiments
between
[@iI
Fig. 1. Crystal
at 500°C
(Atkinson,
200°C
and
3OO’C. Above
boil
(112)
structure
of chakopyrite.
1974;
up to 300°C are inferred to result from the increase in deformation twinning (Kelly and Clark, 1975). Subgrain development was seen to start
Compression experiments on chalcopyrite crystals at room temperature have shown that (112) is the main glide plane (Miigge, 1920; Buerger, 1928; 1930). As in more recent experi-
Cu S Fe S
100 MPa
Arrangement
of atoms and lattice vectors
in (112)
150°C
the
219
experimental pirical
data can be characterized
power
law with
(n = 8.6; Roscoe,
a high
by an em-
stress
exponent
1975).
Starting material The present natural Nababeep
along
of minute
geneities.
single
West Mine,
2). Fractures lines
studies were made utilizing
chalcopyrite
Besides
pores
crystal
Cape Province, (112)
cleavage
Short lattice vectors of chalcopyrite, space group 142d (100) = 0.5291 mn l/2 (111) = 0.6417 mn (110) = 0.7482 nm l/2 (311) = 0.9875 nm [OOl]= 1.0427 nm
the
RSA (Fig. planes
are macroscopic
a larger
a large
from
TABLE 1
polycrystalline
and
Orientation determination
inhomoDue to the pseudocubic
pyrite
chalcopyrite,
Laue
arrangement back
reflection
of atoms
aggregate, sporadic sphalerite grains ( < 30 pm) were found in the undeformed crystal which contains no twins and has a low dislocation density.
in
patterns
along [OOl] and from each other.
(100) cannot be distinguished Reflections of the type h k 21
The chemical composition Cu,,,Fe,,O,S, was established by microprobe analyses and is in good agreement with that of common chalcopyrite, cul.Ol-1.02F%00-1.02 S, (Cabri and Hall, 1972).
and I k 2h have structure factors cubic reflection goniometry the
similar lattice plane spacings and so that they scatter almost like a hkl. By means of X-ray texture orientation of chalcopyrite (Laue
The lattice constants are a, = 0.5291 nm and c,, = 1.0427 nm and thus are up to 0.2% larger than those determined by Cabri and Hall (1972) and Hall and Stewart (1973). Short lattice vectors are listed in Table 1.
group 4/mmm) can be established when a reflection is taken with 1 # 2n and h + k # 2n, cf. 101, 103, 321 (Hennig-Michaeli and Herres, 1985). These weak reflections are superstructure reflections when compared to sphalerite. The 103 reflection has been used in the present work. The Liicke-texture goniometer plots pole diagrams in stereographic projection (Fig. 3). Specimen preparation During cutting and polishing the chalcopyrite crystal behaves in a brittle manner. The crystal was embedded in araldite such that the crystal directions [221], [321] and [02i] were parallel to the edges of the araldite block. The embedded crystal was cut parallel to (112) into two pieces by a rotating grinding blade (thickness 1.7 mm, u = 32 m s-l) which is usually employed to slice stressfree optical glasses. From one piece several slices parallel to (li0) and (012) were cut off in a high precision hole saw (blade thickness 200 pm, u = 25
Fig. 2. Natural chalcopyrite single crystal. Nababeep West Mine, Cape Province, RSA. On the top of the crystal an inclusion of a pyrite aggregate. Scale mark 1 cm.
m s-l). The slices were mounted between glass plates and prism-shaped specimens (7 x 7 x 14 mm3) were cut by a low speed diamond saw. Three of the four prism surfaces were grounded (Sic) and polished (Al,O,) by hand with successively finer grades down to < 1 pm. Surface cavities could not be removed in all cases (see Fig. 8c,
220
Fig. 3. Orientation CoK,
= 35.9O)
projection
from
determination (001) and
(SP), upper hemisphere
of chalcopyrite (100) faces.
(Laue
Besides
symmetry
103 reflections,
4/mmm).
Liicke
112 reflections
pole
figure
(2@ CoK,
goniometer
plots
= 34.2O) appear.
of 103 (26’ Stereographic
(UH).
d). The polished surface areas were checked by interference contrast observations to be free from fine scratches. After re-exa~nation of the orientation a specimen coordinate system x, y, z was defined for each crystal (see Figs. 8a, 9a, lOa). Experimental procedure
The program assumes homogeneous axial strain which, in reality, never occurs during single crystal tests of this kind. In particular, in this series of experiments the strain is usually concentrated in coarse slip bands distributed inhomogeneously within the crystal. Thus the stress-strain diagrams outline but do not clearly define the deformation behaviour.
Apparatus Compression The triaxial compression apparatus used in this series has been previously described in detail (Bauer, 1973) and briefly sketched (HennigMichaeli and Siemes, 1982). The confining pressure medium is silicone oil. The test sample is encapsuled in an aluminium jacket and a platinum foil is inserted between the chalcopyrite and the aluminium to prevent surface reactions and to make easier removal of the jacket from the deformed crystal. The jacket is fixed to conical end pieces by steel rings.
Measurements During the run, load, displacement, and confining pressure are recorded in chosen time increments (60 s). The rate of displacement is approximately kept constant by regulation of the load increment. Stress-strain curves are derived from the data records by means of a computer program taking into account the specimen dimensions and the elastic distortion of the apparatus.
tests on chalcopyrite single crystals
All experiments confining pressure
were performed at 300 MPa as previous experiments, cited
above, had shown that up to 200 MPa the strength of chalcopyrite is dependent on confining pressure. The temperature of deformation was 200°C (0.41 T,) and the strain rate about 4. 10m6 s-r. There was not any evidence of phase transformations or de-sulph~~on during the experiments. Eight different orientations-[OOl], [IOO], [lIO], [ill], [021], [221], [421], [821]-were tested. In Fig. 4 the size of the circles representing the compression axes approximately characterizes the range of inaccuracy in the crystal o~entation as determined by texture goniometry. The permanent axial shortening of the samples was between 0.7% and 2.3% (see Table 4). The samples were only deformed to this extent as experience has shown that at low permanent strains the glide line patterns on the crystals can be more readily analyzed than those on strongly deformed specimens. In addition the determination of
221
Determination of glide modes
Fig 4. Crystallography of chalcopyrite. SP. Planes and directions (black points), compression axes (open circles).
Burgers vectors by TEM is facilitated if there is only a moderate dislocation density within the deformed crystal. The stress-strain curves display a marked anisotropy of the plastic behaviour of chaleopyrite (Fig. 5). “Weak” directions are [NO] and [021], “strong” directions are [llO], [OOl] and [221]. Marked strain hardening characterizes the [ill] direction whereas, in the [OOl] direction, the curve seems to indicate steady-state flow behaviour.
Conditions: T
= 200°C
pc = 300 MPa E
0
I’ 0
= 4.10-6s“
I
I
I
I
I
05
1
15
2
25 E I%1
Fig. 5. Stress-strain
curves of chaicopyrite single crystals.
In order to understand the plastic behaviour of a crystal, careful observation of the surface structures is required, as it gives fund~ent~ evidence of the material displa~m~t during deformation. The aim of the present work is to determine the glide modes by analysis of the strained crystals. The assumption was made that the glide planes are low index lattice planes and that the glide directions are low index lattice directions with a small Burgers vector. Hypothetical and crystallographically non-equivalent glide modes of this kind are listed in Table 2, together with the S&mid factors for the eight compression directions used in these experiments. In this study defo~ation twins were distinguished from slip lines by measuring the 112 reflection in the X-ray pole figure goniometer (Fig. 10e). Glide planes, glide line structures
When there are prominent sets of glide lines that can be traced from one surface to an adjacent one, it is possible to determine the glide plane by the angles they make with the edge between the two surfaces (Reed-Hill, 1968). In all specimens glide on (112) has been the predominant deformation mechanism. There are two different kinds of (112) glide lines. Very coarse straight bands characterize slip, whereas (112) deformation twins are more or less wavy depending on the surface they occur on. On the [OOl] specimen only (112) twins have been observed. In. all other samples {1123 slip is prevalent. On the [221] oriented specimen homogeneously distributed wavy glide lines indicate another slip plane in the zone ]liO] and in the [llO] sample faint short lines in more strongly deformed areas suggest a slip plane in the zone [OOl]. On all specimen surfaces the (112) slip bands are of the same kind. They are always straight and indicate a planar slip behaviour. The thickness of the bands varies up to maximum of 40 pm. This is interpreted to indicate a mechanism of dislocation multip~cation in adjacent slip planes so that the
222
223
overall
slip occurs in sets of closely spaced planes.
Between
the slip bands
fected by deformation The
exterior
the material
appears
Y
unaf-
tanIp
(e.g., see Fig. 9c, d).
of the
(112)
slip
bands,
trace
con-
= of
a, / ey glide
direction
sistently similar on all surfaces, suggests that { 112} slip in all specimens was due to the same or almost
the same slip mode. To determine
direction,
the slip band characteristics
the slip
were studied
in detail. Determination
Fig. 7. Crystal distortion.
Extensions
e,,
e., along the speci-
mens axes x, y indicate the direction of the trace of the main glide direction in the x-y
plane + = dy,
trace of glide direc-
tion.
adjacent specimen faces allow an estimation of the angular range of the slip direction on a particular
of the slip direction in (112)
Owing to the coarse character of the (112) slip bands the sense of the slip steps on the prepolished surfaces can be easily determined by interference contrast optical microscopy. The sense of the slip steps indicates whether at a slip band the part of the crystal above the line (sense a) or the part of the crystal below the line (sense b) is displaced towards the observer (Fig. 6). When the slip plane is known the senses of the slip steps as observed on the two adjacent crystal faces allow assignment of the direction of material transport and, thus, the direction of the Burgers vector, to a specific quadrant in the stereogram of the crystal top face. The height of the slip steps further confines the possible slip directions. The slip steps are of small height and display a weak relief when the slip direction is oriented close slip steps and a stronger slip direction at a high surface. The relative relief
to a surface and higher relief is produced by a angle to the specimen of sets of slip lines on
slip plane. Crystal distortion After deformation the dimensions of the crystals were remeasured. The shortening e, along the compression axis z as well as the extension e,, ev normal
to the prism
faces provide
the basis
of
determining the bulk material transport during deformation. The ratio eJe,, is an approximate measure of the anisotropy of plastic strain. If only one predominant (112) slip system in a crystal has been active, the angle r$ (Fig. 7) indicates the direction of the trace of the glide direction in the x-y-plane. Determination (CRSS)
of the critical resolved shear stress
The yield strength of the crystal is taken as the stress at the first strong departure from the elastic portion of the stress strain curve. The glide system, represented by the highest density of glide lines on the crystal the CRSS: Identification
surfaces,
is used to determine
of slip systems
in the deformed
crystals Three examples of deformed single crystals have been selected to illustrate how the glide modes have been determined.
Fig. 6. Sense of glide steps. Sense a: the part of the crystal
Compression
axis [l 1 O]
Specimen y = [OOl].
axes (Fig.
(I bove the line is displaced towards the observer; sense b: the part of the crystal observer.
below
the line is displaced
towards
the
8a):
z = [llO],
x = [ilO],
224
L
f
[1101
11
X
b
Malt. slip A
a
d
,1
mm
,
pole
plane
225
Crystal distortion The main slip system on (112) chiefly caused the crystal distortion. The strain due to other slip systems is negligible. Due to the symmetrical arrangement of the slip planes (112) and (112) to the [llO] compression axis, a specific hypothetical {112} slip mode would produce identical ex/eY ratios whatever the slip mode, e.g.:
Slip-line pattern (Fig. 8c-fl On the (ilO) surface four kinds of (112) slip lines are apparent indicating that four different slip systems have been activated. The morphology of the lines are the same in aII cases; they are straight and more or less coarse. The slip bands are directed along (112) and (112) traces. In each direction, sets of lines with mutually opposite senses a and b are present, indicating that two different slip systems were activated on one plane.
(112) (iii)
Main slip system Most prevalent are slip bands on (112) with sense a on the surface (ilO>. They extend across the whole specimen and display a rather strong relief on both specimen surfaces, (710) and (001) (Fig. 8c-f). The slip direction of the chief lines on (112) is situated in the orientation range x--J-t as represented by the upper right quadrant of the stereogram in Fig. 8b on the upper hemisphere. Low index directions in (112) with positive S&mid factors and with a corresponding orientation are [ZOi), [?li] and [42i]. [iii] is parallel to the (ilO) surface and would not have produced a marked relief on it (Table 3).
a. Specimen
crystal,
compressed
axes, orientation
(201)
= 0.70
(311)
= 1.37
(421)
= 2.05
Slip mode An unexpected result of this experiment was that {112}@1) slip is not a prominent slip mode (under the given conditions) although 1/2(iil) is the shortest lattice vector in (112) with a high S&mid factor (0.47) in this experiment. (112) (311) slip explains best the observations, but {112}(201) cannot be excluded from being an active slip mode. Crystal strength The [llO] specimen was the strongest of the whole series (Fig. 5). The plastic deformation proceeded discontinuously at growing stress levels. The unsteady plastic behaviour is assumed to correspond to ,the sudden formation of individual slip bands. Each slip band seems to have a specific yield point. The yield strength of the crystal is
along [llO].
of the unit cell.
b. Top face of the crystal. SP/UH. Pole and trace of the main slip plane (ll?). The slip direction -X-y-z. The direction [311] agrees best with the relief of the main lines and the crystal distortion. c. Face (ilO), reflection
micrograph.
Strong
d. Face (OOl), reflection
micrograph.
Medium
e. Detail
from (c), interference
contrast
dark lines are of sense n, due to (llj)[%i] of sense b, due to (112)[131] f. Detail from (d), interference slip. In the heavily
deformed
=0
The ex/ey ratio (1.23) of the deformed crystal most closely fits (311) and hence the main slip system is most likely to be (112) [jli].
Deformation twins Minor twins along (112) and (172) as identified by X-ray texture goniometry are parallel to the compression axis and are thought to be due to stress inhomogeneities at surface imperfections. They are more abundant on the unpolished surface (170) and absent on the polished surfaces (001) and (110). On (OOi) they appear in the surroundings of surface cavities.
Fig. 8. Deformed
eJe,
slip. Faint contrast
(negative
end) lies in the quadrant
Slip mode is {112}(311).
relief of main slip bands. relief of slip bands.
micrograph.
Slip lines along (112) (N55“E)
are due to two different
slip. The light lines of sense b, due to (llz)[l%] traces (E-W) micrograph.
area faint inclined
may indicate
the are
slip on a plane in the zone [OOl], perhaps
All coarse dark slip lines (E-W)
slip traces occur.
(112) slip systems:
slip. Slip lines along (112) (N54OW) {lOO) (010)
are of sense b, due to (ll?)[%i]
slip.
and (ll?)[l?i]
3
Schmid
factors (S) deviate
0.41
[ZOi]
0.48
]jii]+
0.45
slip modes
0.32
]5ii]-
*
’
‘
3ii, 4%)
ones in Table 2.
[iii]-
i
iii).
or of (112}(11i)
0.25
]42i]
0.24
--[Ill].
0.27
[ilo]
0.24
(S)
chakopyrite
Schmid factors
{ 112}(201,~11.421,
from the theoretical
possible
’
0.42
[Zoi]
0.42
[421]
0.32
[4Zl]
0.43
[zoi]
0.37
[ZCij-
0.39
[ZB] -
and experimental
on the deformed
slip modes {112)(2Oi,
]3ii]+
0.37
]3ii]+
0.48
]3ii]-
0.32
0.41 --]3111 0.3% --[131].
possible
slightly
of hypothetically
Experimental
[ uw] ’ is a shear direction
S
S
s
S
s
s
S
of hypothetically
(112)
(112,
(1lZ)
(ii2)
(112)
(ii2)
(i12)
s
--[131]
Possible shear directions
is a shear direction
* [UWJ
I1101
CHX
]lW
CH6
[X211
CH5
]42Ti
CH4
WI
CH3
12211
CH2
11111
CHl
(ii2)
plane
pression
axis
Main
slip
of sense of shear at the main sets of {112} slip bands
Cry&II,
analysis
com-
Two-surface
TABLE *
-twins.
s
S
S
S
s
S
s
s
Excluded
crystals
[iii]-
[201]+
0.48
[iii]
0.49
]42i]
0.46
@oi]+
0.42
+
1
[iio]
0.41
]oZi]
+
0.30
[iii]
[Z41] 0.23
[ilo] 0.41
0.20
[02i].
’
-_[ill] 0.38
[021] 0.29
[ill]*
0.24
[241]
0.28
toii]
0.41
0.42
]4Zi] 0.4Y
0.30
]iio]
0.33
iZ;ii]
*
+
’
[ii01 0.28
[iii]0.29
0.28
[iio]
[Ioil
0.31
0.38
0.40
]o%]
shear directions
221
265 f 5 MPa and the CRSS for the most likely slip mode (112) (311) is about 85 MPa. Compression
axis [021]
Specimen axes (Fig. 9a): z = [021], x = [02x], y = (ioo]. Slip line pattern
(Fig. SC-~).
The slip line pattern appears similar to that of the [llO] sample. However, there are only two kinds of (112) slip bands, one predominant set along (112) and minor slip lines along (712). Comparison of the relief of lines on the two specimens (Figs. 8 and 9) gives evidence of a remarkable difference: Whereas on the [llO] sample the lines appear in almost the same contrast on both surfaces, on the [021] sample the relief is weak on the (012) face and very strong on the (%lO) face, indicating that the direction of slip is close to the (012) face. Minor twins on (712) have been detected by texture goniometry of this sample. Main slip system
On the face (012), the (112) lines are of sense a (Fig. 8e). The slip direction is, again, situated in the orientation range Z-y-z (upper hemisphere, Fig. 9b). Possible slip directions might be [3ii] and [2Oi], but the relief due to a direction close to (Olz), excludes [2Oi].
observations is [3‘ii] and hence {112}(3ii) most likely the slip mode. Crystal strength
The [021] crystal was one of the weakest crystals in the test series (Fig. 5). A stepwise shortening characterized the plastic behaviour Iike in the [llO] crystal, pointing to a corresponding slip behaviour. The yield strength, 175 + 5 MPa, is only two thirds of that of the [llO] crystal. The CRSS for the main slip system, (112) [3ii], is about 84 MPa. The CRSS value, the corresponding slip behaviour and the consistent attributes of the slip bands, in either specimen,- respectively corroborate -the postulation that (112)[311] was the predominent active sIip system in the [llO] specimen. The close agreement of the ratio (0.67) of the reciprocal S&mid factors of the main slip systems in the two samples with the ratio of the yield strengths u,,~OZll/~,,ulOl = 0.66 is believed not to be simply fortuitous. It supports the following conclusions concerning the plastic behaviour of chalcopyrite under the experimental conditions: (a) {112}(~11) and {112}(3ii) are the main slip modes. (b) Although the two slip modes are not crystahographicahy equivalent they have nearly identical CRSS. (c) The S&mid law is obeyed. Compression
Crystal distortion
A strong anisotropy of lateral extension corresponds to the observed surface pattern. eJe,, = 0.23 = arctan 13” only fits the direction [3ii] (Fig. 8b). Slip mode The sense of surface steps excludes [ilO] from
being slip direction. The (llZ)[liO] system was not activated. (112)[2Oi] does not explain the slip band exteriors or the crystal distortion. If {112}(201,2Oi) slip had operated in the two crystals that have been described, the deformed samples would look almost identical. The only direction in (112) that closely fits the
is
axis [l I l]
Specimen axes (Fig. lOa): z = [ill], y = [El] Glide line pattern
x = [ilO],
(Fig. 10~)
Five different sets of glide lines occur, two along (i12), two along (112) and one along (112). Main slip systems
Two sets of long, straight lines result from slip on (112) and (112). They display a distinct relief on both specimen faces. On the (ii2) surface, both sets of slip lines are of sense a. This therefore unequivocally excludes (2Oi) to be slip direction. Although [?Oi] on (i12) and [O%] on (li2) are directions of high Schmid factors in this test
228
a
e
b
ccl12 X
Main slip plane A pale
229
TABLE
4
Compression
tests on chalcopyrite
Sample
Compression
Maximum
Shorten-
Yield
axiS
strength
ing
stress
(MPa)
(W)
(MPa)
265
1.42
180
WI
CHl
single crystals
(temperature
200°C,
confining
pressure
300 MPa, strain
Glide modes
{i12}(3ii) dip
rate about
4. 10m6 s-l)
Schmid
CRSS
factor
(MPa)
0.41
74
(112}(lli)twinmng CH2
[22ll
287
2.27
250
(ll2)(3ii)
dip
0.32
80
{001}(110)
slip (TEM)
0.47
i 120
CH3
[02ll
196
1.00
175
(ll2)(3ii)
dip
0.48
84
CH4
14211
242
1.10
220
{112}(311)
slip
0.37
81
{ll2)(3ii)
dip
CH5
WI
186
0.65
165
{112}(311)
slip
0.45
74
CH6
WI WI w11
186
1.13
165
(112}(311)
slip
0.48
79
294
1.13
265
{112)(?11)
slip
0.32
85
261
1.58
250
{112}(111)twinmng
0.46
115
CH8 CHlO
Crystal strength The yield strength of the sample is low, 180 f 10 MPa, but the strong strain hardening is singular in this test series. In the range of yielding an unsteady flow was observed, but during strain hardening the flow was continuous. The CRSS for {112}(3ii) slip is about 74 MPa and, thus, in agreement with the values obtained from the other crystals (Table 4) within the experimental uncertainties. The interaction of slip and twinning may have caused the more continuous plastic flow as well as the strain hardening.
(Table 3), they have not been slip directions because they are oriented parallel to the (ii2) surface and cannot have produced the marked relief as observed (Fig. 10~). {112}(1iO) can also be excluded, because it would not have produced a strong line relief on the (710) surface. Therefore the best agreement with the observed slip line structures are the two slip systems (i12) [‘;ii] and (172) [i?i], both belonging to the slip mode {ii2)(3ii). Deformation twins X-ray texture goniometry reveals three different orientations of deformation twins (Fig. 10d): (i12), (172) (112) are the twin planes. The exterior of the twins differs markedly from that of the slip lines. The twins are short and wavy. On the (ii2) surface the twins on (i12) and (172) are of opposite sense in comparison to the slip lines (Fig. SC) and agree with (il2)[ili] and (li2)[lii] deformation twinning. {112) (11-i) is the twinning mode. Fig. 9. Deformed a. Specimen
crystal,
compressed
axes, orientation
sullunaly of results Slip modes Slip on (112) was the main deformation mechanism in all specimens except the [OOl] oriented sample. Coarse and straight slip bands indicate a planar slip behaviour. The uniform appearance of slip bands on all respective deformed crystals sug-
along [021].
of the unit cell.
b. Top face of the crystal.
SP/UH.
X-y-z.
agrees best with the relief of lines and the crystal
The direction
[3ii]
Pole and trace of the main slip plane (112). The slip direction
c. Face (Olj), reflection
micrograph.
Weak relief of main slip bands.
d. Face @IO), reflection
micrograph.
Very strong
e. Detail from (c), interference
distortion.
(negative
end) lies in the quadrant
Slip mode is (112}(3ii).
relief of slip bands,
contrast
micrograph.
Slip bands
f. Detail from (d), interference contrast --are of sense a, due to (i12)[311] slip.
micrograph.
Light slip lines (N86 o W) are of sense b, due to (112)[3ii]
along (112) (N55OE)
are of sense a, due to (112)[3ii]
slip.
slip. Dark slip lines
230
b
a
Main glide planes .
poles traces
,
C
Fig. 10. Deformed a. Specimen
crystal,
compressed
axes, orientation
b. Top face of the crystal. directions
200
IUrn
,
d
‘1
along [ill]
of the unit cell. SP/UH.
Poles and traces of the main glide planes
(i12),
(112). (112): slip directions
(s) and twinning
(tw) are indicated.
c. Detail of face (ii2),
interference
contrast
micrograph.
(712) traces (N31°E).
Slip lines are dark and of sense a, due to (i12)[%i]
slip. Twins are light and short and of sense b, due to (i12)[111] twinning. (112) traces (N32O W). Slip lines are dark and of sense a, -__ due to (li2)[131] slip. Twins are light and of sense 6, due to (liZ)[lTi] twinning. (112) traces (E-W). Wavy twins are light and of sense b, due to (112)[11i]
twinning.
d. 112 pole figure goniometer twinning. (il2)
twins:
B-A&C_B-D_B.
(li2)
twins:
C-A_C-B_C-D_C.
(112) twins:
D-A&B_D-CLJ.
plot, face (ii2).
SP/UH.
Host crystal
orientation
is A-B-C-D.
Double
symbol
reflexes
are due to
231
gests a unique operating (112) slip mode. AnaIysis of the senses of slip steps on mutually perpendicular prepolished faces of the prism-shaped samples allows us to exclude other possible slip directions in the principal slip planes (Table 3). The shear along the slip bands and the distortion of the crystals are in accordance with {112}(311) slip or pi2)(3ii) slip, respectively. The anisotropy of yield strength is in agreement with these conclusions. The CRSS is about 80 MPa (Table 4). The Burgers vector l/2(311) is large and moving dislocations should be dissociated. TEM-studies on the samples [llO] and [221] (Couderc and Hennig-Michaeli, 1986) show that the majority of dislocations in (112) remain in contrast whatever the operating g is. Dissociation into up to four partials is observed in weak beam dark field micrographs. Such peculiarities can be explained by the Burgers vector b = l/2(311) although a full characterization of these dislocations has not yet been accomplished. In the [221} oriented crystal (OOl)(llO) slip has been identified by TEM-observations (Couderc and Hennig-Michaeli, 1985). Some cross slip from (001) to (112) occurs, thus explaining the waviness of the corresponding slip traces on the specimen surface. On the [llO] sample faint surface traces may indicate a slip plane in the zone [OOl]; they are possibly due to (100) (010) slip (Fig. 8e). In the vicinity of surface inhomogeneities, minor slip lines, mostly along (112) traces, do not agree with the shear due to the main slip modes. Deformation
twinning
{112}(11i) deformation twinning was the principal deformation mechanism in the [OOl] sample and important in the [ill] sample. K, is not yet known but with analogy to sphalerite it is assumed to be (ii2). The state of the specimen surface obviously has an effect on the origin of (112) twins. X-ray texture goniometry shows that twins are more abundant on non-polished surfaces than on prepolished ones. On prepolished surfaces they tend to start at surface inhomogeneities, e.g., cavities.
On the [221] oriented crystal, twins proceed from the (110) (110) surfaces, but are nearly absent on (114) and (ii4). The twins are long and straight on surfaces parallel to the twinning direction and short and wavy on faces mutually perpendicular. Thus, the shapes of the twins resemble blades of swords, the twinning direction representing the long axis about which the blade is wrinkled. From the shape of the twins, it can be inferred that {112}(11i) twinning dislocations can move easier if they are of edge character than if they are screw dislocations. TEM-studies reveal numerous immobile screw segments of twin dislocations pinned at the boundaries of microtwins (Couderc and HennigMichaeli, 1986). Twinning, as a unique glide mode does not give rise to any strain hardening, as displayed by the flow behaviour of the [OOl] sample. The interaction of slip and twinning has probably caused the strong strain hardening in the [ill] sample. The twins in the [ill] crystal originated at lower shear stresses (< 85 MPa) than those in the [OOl] crystal (115 MPa). These results show that there does not seem to be a CRSS for this type of mechanical twinning in chalcopyrite. Discussion
The slip modes {112}(311) and {112}(3ii) are the models which explain the experimental observations better than all other hypothetically possible slip modes on (112). Contrary to expectations, (112) slip in chalcopyrite agrees neither with the shortest Burgers vector 1/2(iil) in {112}, nor with the previously predicted slip directions (110, 021). Such {112}(liO, 021) slip postulates pseudocubic slip behaviour which would have given rise to similar results for the compression tests on [OOl]-[loo], [ill}-[421] and [llO]-[021]. The experimental results are not at all consistent with this “sphalerite-like” model, but indicate that the deformation mechanisms are controlled by the tetragonal lattice and, hence, by the cation sublattice.
232
Acknowledgements
The Deutsche Forschungsg~me~s~haft supported this research and placed at our disposal the deformation equipment and the texture goniometer. A.F. Lombaard and Mr. Engelbrecht (Ookiep Copper Company) supplied the single crystal. G. Neidull (Ernst Leitz Wet&r GmbH) and H. Oepen (Philips Research Laboratory, Aachen) helped to cut the crystal. The staff of the Mineralogical Institute rendered practical assistance, in particular A. Wiechowski, B. Thiele (microprobe analysis), G. Siebel (X-ray diffraction), W. Grawinkel (poising), G. Prapotny, M. Brandt (apparatus), M. Jansen (photographs) and 3. Huppertz (crystal preparation and data processing). The work benefited from discussions with N. Herres, H.C. Heard, L. Martens, L. Kiibler and J.J. Couderc. The help of these persons and institutions is gratefully acknowledged. Thanks are due to two anonymous referees for their constructive criticism of the manuscript. References Atkinson, B.K., 1974. Experimental deformation of polycrystalline galena, chalcopyrite and pyrrhotite. Inst. Min. Metall. Trans., Sec. B, 83: B19-B28. Bauer, G., 1973. Experimentelle Stauchverformung an otztaler Glimmerschiefem. Diss. Rheinisch-WestfUischen Hochschule Aachen, 127 pp. Buerger, M.J., 1928. The plastic deformation of ore minerals Am. Mineral., 13: 35-51. Buerger, M.J., 1930. Translation gliding in crystals. Am. Min., 15: 45-64. Cabri, L.J., and Hall, S.R., 1972. Mooihoekite and haycockite, two new copper-iron sulfides and their relationship to chalcopyrite and talnakhite. Am. Mineral., 57: 689-708. Couderc, J.J. and Hennig-Michaeli, C., 1985. Evidence for (001) (110) slip in experimentally deformed chalcopyrite by TEM-observations. Forts&r. Mineral., 63 (Beih. 1): 45. Couderc, J.J. and Hennig-Michaeli, C., 1986. Transmission electron microscopy of experimentally deformed chalcopyrite single crystals. Phys. Chem. Miner., 13: 393-402.
COX,SF. and Etheridge, M.A., 1984. Deformation microfabric development in chalcopyrite in fault zones, Mt. Lyell, Tasmania. J. Struct. Geol., 66: 167-182. Hall, S.R. and Stewart, J., 1973. The crystal structure refinement of chalcopyrite, CuFeS,. Acta Cryst., B29: 579-585. Hennig-Michaeli, C. and Herres, N., 1985. Orientierungsbestimmung experimentell erzeugter Deformationszwillinge nach (112) und {102} im Chalcopyrit &Fe% mit Hilfe des Lbcke-Texturgoniometers. Forts&r. Miner., 63 (Beih. 1): 94. Hennig-Michaeli, C. and Siemes, H., 1982. Experimental deformation of hematite crystals between 25’C and 400°C at 400 MPa confining pressure. In: W. Schreyer (Editor). High-pressure Researches in Geoscience. Schweizerbart, Stuttgart, pp. 133-150. Kelly, W.C. and Clark, B.R., 1975. Sulfide deformation studies. III. Experimental deformation of chalcopyrite to 2000 bars and 500°C. Econ. Geol., 70: 431-453. Kom, D., 1933. Ein deformiertes Flusspat-Quar-Kupferkiesgefbge aus einer mittelschwedischen SulfidlagerstBtte. Neues Jahrb. Mineral., Geol., Pahaontol., Beil., A66: 433-459. Lang, H., 1968. Stauchversuche mit poly~$t~~nen Kupferkiesen und deren Ergebnisse unter Beticksichtigung der Gefigeregelung. Diss. RWTH Aachen, 131 pp. MUgge, O., 1920. ijber Translationen am Schwefel, Periklas und Kupferkies und einfache Schiebungen am Boumomt, Pyrargyrit, Kupferglanz und Silberkupfer~~. Neues. Jahrb. Mineral., Geol. Pal%ontol., pp. 24-54. Paul& L. and Brockway, L.O., 1932. The crystal structure of chalcopyrite CuFeSz. Z. Kristallogr., 82: 188-194. Ramdohr, P., 1980. The Ore Minerals and Their Intergrowths. Pergamon Press, London, 2nd ed. 1205 pp. Reed-Hill, R.E., 1968. Crystallographic techniques to determine the indices of slip and twinning. In: R.F. Bunshab (Editor), Techniques for the Direct Observation of Structure and Imperfections. In: Techniques of Metals Research, Vol. II, Part 1. Interscience, New York, N.Y., pp. 257-290. Roscoe, W.E., 1975. Experimental deformation of natural chalcopyrite at temperatures up to 300°C over the strain rate range lo-’ to 10v6 s-r. Econ. Geol., 70: 454-472. Shadlun, T.N., 1953. The change in the structure of aggregates and in the internal structure of grains of chalcopyrite subjected to the influence of dynamic factors. Mineral. Sb., Lvov. Geol., Ser. 7: 75-80. Shuey, R.T., 1975. Semiconducting Ore Minerals. Elsevier, Amsterdam, 415 pp.